Q: I forgett security qustion

You need to ask Apple's Account Security team to reset your security questions. To contact them, click here and pick a method; if that page doesn't list one for your country or you're unable to call, fill out and submit this form.

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If you have a verified rescue email address on your account (an additional/alternate email address is different) you can use that to reset them : If you forgot the answers to your Apple ID security questions

If you don't have a rescue email address you will have to contact Support in the country where you are (and which is therefore the country on your account) to get the questions reset - from the above link :

If you can't reset your security questions

If you can't send a reset email, don't have a rescue email address, or can't access email at your rescue email address, call us for help. When you call, you might need to create a temporary support PIN to verify your identity. After you reset your security questions, you might want to update your rescue email address.

If your country isn't on that ‘call us for help’ page then try this form to contact Support : https://www.apple.com/emea/support/itunes/contact.html

From what I understand, you are trying to reset the security questions to your Apple ID to be able to purchase something from the App Store, iTunes Store or iBook Store. If that is the case, read this article :

If you forgot the answers to your Apple ID security questions - Apple Support

Basically, if you set up a rescue email, you can sign in to your Apple ID and reset the security questions by yourself. If you haven't, or if you do not have access to your rescue email, you will need to call Apple Support while you have access to the Internet.